The present invention relates to a wireless terminal according to the preamble of the appended claim 1, and to a method according to the appended claim 8, for coupling a wireless terminal to a data transmission network.
Considerable growth in the use of computers has increased the need for establishing data transmission networks, to which these computers are coupled. Especially in office use, a local area network, such as the so-called Ethernet data network, is used as a data transmission network, to which office computers, printers and other corresponding devices are connected. Thus, it is possible to use other resources connected to the local area network from the computer, for example for printing, wherein it is not necessary to provide each computer with such peripheral devices. The computer connected to the local area network contains a network interface card, or the like, which comprises means necessary for establishing a data transmission connection between the computer and the local area network. Inter-office local area networks are typically implemented by means of a landline, for example by using a so-called thin Ethernet cabling. With the thin Ethernet cabling it is possible to achieve a speed of 10 Mb/s, but for example with twin cabling, it is possible to use transmission speeds of even 100 Mb/s.
It is also possible to implement the local area network as a wireless local area network WLAN. These wireless local area networks are typically based on the use of radio modems, wherein the office can be included in the range of the local area network with one or more such radio modems. The computer is equipped with a network interface card, which comprises, for instance, a radio transceiver for setting up a connection to a radio modem in the local area network. In such a wireless local area network, the placement of the computers is consirerably freer compared to a fixed landline local area network. Such landline local area networks intended for office use use in a relatively large bandwidth, wherein it is possible to achieve data transmission rates as high as 2 Mb/s. In particular, it is easy to connect portable computers to such a wireless local area network.
In addition to the above presented local area network solutions, the global Internet data network is known, which has recently grown very rapidly in popularity. The aforementioned local area networks can constitute a part of such Internet data network, wherein a data transmission connection to the Internet data network is set up from the local area network LAN, WLAN. Such a data transmission connection can be, for example, a modem connection from the server computer of the local area network to the server computer of Internet operator, or the server computer of the local area network can be coupled to form a part of the Internet data network.
In connection with portable computers, so-called PCMCIA cards have been developed, which contain built-in mobile station features, such as a GSM mobile station and peripheral circuits required for data transmission. Thus, it is possible to set up a data call from such a wireless data processor via the GSM mobile communication network to another data processor or even to a local area network of an office. Previously, a restriction in such data transmission utilizing the GSM mobile communication network has been the relatively low data transmission rate of 9600 bits/s, but solutions capable of faster data transmission are under development, such as HSCSD (High Speed Circuit Switched Data) and GPRS (General Packet Radio Service). The appended FIG. 1 presents in a reduced skeleton diagram the aforementioned different network types.
As portable computers are becoming smaller in size and their features are increasing, it has become more and more popular to use them also in offices. A portable computer, provided with a network interface card intended for use in a wireless local area network, can be used as a wireless terminal in connection with the wireless local area network WLAN. The local area network of an office can consist of both a landline local area network LAN and a wireless local area network WLAN. For example, upon enlargement of the office, a fixed interconnection is not necessarily made for the local area network, but the extension of the local area network is implemented with such a wireless local area network solution in the office. In the office, the terminal could thus primarily use the landline local area network, wherein a network interface card for the landline local area network is connected to the portable computer. To make better mobility possible, a network interface card for the wireless local area network is changed in the portable computer. At this stage, however, the user of the terminal has to terminate the network connections in use at that moment and change the network interface card, after which the connection to the local area network can be set up again. In some situations, it might be necessary to use the terminal outside the office and be connected to the local area network of the office. Thus, when using methods and local area networks currently known, it is possible to change the network interface card in the portable computer whereby the connection can be set up via a mobile communication network. Also in this situation it is not possible to change the connection by using methods and terminals of prior art without terminating the active connections.
Furthermore, a problem in the different communication networks presented above is, for instance, that in each communication network, a different terminal identification is used. Differences in the terminal identification used by different data transmission networks do not necessarily cause inconveniences for the user of the terminal, because s/he is always aware of which network s/he is using. Nevertheless, when an attempt is made to set up a connection to this terminal, the person who sets up the connection to the terminal has to know the location in the communication network to which the terminal in question is connected at a given time. One such connection set-up situation is when an attempt is made to set up a call via the Internet data network. Another drawback is that the user of such different data transmission networks has to monitor the quality of the connection. For example, when the user moves inside the office and uses the wireless local area network WLAN, in some parts of the office the quality of the connection may become so poor that data transmission is disturbed or delayed significantly. Thus, the user should try to shift to such a data transmission network, in which a better connection quality is achieved, for example to a landline local area network LAN, if such is in the vicinity, or to the GSM mobile communication network, if the user is in its coverage area. This change of the data transmission network causes the problems described above: termination of the existing connections, setting up new connections and, if necessary, also cutting off or setting up a telephone connection.
It is a purpose of the present invention to provide a method for coupling a portable terminal in a flexible manner to a data transmission network, and for changing the data transmission connection used at a given time to another data transmission network when necessary, as well as to a portable terminal according to the method. A wireless terminal according to the present invention is characterized in what will be presented in the characterizing part of the appended claim 1. A method according to the present invention is characterized in what will be presented in the characterizing part of the appended claim 8. The invention is based on the idea that the network layer address (IP address) of the terminal and the link layer addresses used by the different network interface solutions available in the terminal are combined in the terminal.
With the present invention, significant advantages are achieved, compared to methods and terminals of prior art. The embodiment according to the invention makes it possible to supplement the operating system used in the terminal with the functionality of a mobile terminal, without a need to make changes in the operational modules of the operating system or in the network interface software. Thus, such a multi-mode terminal can be used in several local area networks of different types and in other communication networks, and even in such a way that the communication network used at a given time can be changed without terminating active connections. This transition can be arranged to be conducted in such a way that the user does not even notice the transition. Thus, it is possible to use one network layer address in the terminal, wherein it is not necessary for the applications used in the terminal to know which physical data transmission network is used at a given time. This invention also makes it possible to use of all the data transmission networks available at a time, the data transmission network, in which the best possible connection quality is achieved. In addition, when the quality of the connection possibly becomes poor, the data transmission network can be changed to another data transmission network, in which a better connection quality is possibly achieved at that moment. Also, the user of the terminal according to the invention can always be communicated without the initiator of the communication having to know to which data transmission network the terminal is coupled at a given time.